As the above-described appearance inspection apparatus, for example, an apparatus disclosed in the Japanese Unexamined Patent Application Publication No. 61-211209 is known conventionally.
This inspection apparatus has a hopper for receiving a large number of inspection objects, a vibratory feeder for linearly conveying the inspection objects discharged from the lower end of the hopper, a flow straightening mechanism for aligning the inspection objects conveyed by the vibratory feeder in a row and discharging them, a first conveying device for conveying the inspection objects discharged from the flow straightening mechanism while supporting the lower surfaces thereof, a second conveying device for conveying the inspection objects conveyed by the first conveying device while sucking the upper surfaces thereof, a third conveying device for conveying the inspection objects conveyed by the second conveyed device while sucking the lower surfaces thereof, a first imaging device for imaging the lower surfaces of the inspection objects being conveyed by the second conveying device, and a second imaging device for imaging the upper surfaces of the inspection objects being conveyed by the third conveying device, and a sorting device for analyzing both of the images of the upper and lower surfaces of each inspection object which are captured by the first imaging device and the second imaging device, judging the qualities of the upper and lower surfaces, and sorting the inspection objects according to the judgment results.
According to this inspection apparatus, first of all, a large number of inspection objects are thrown into the hopper. Then, by the vibration of the vibratory feeder, the inspection objects thrown in are discharged in turn from the lower end of the hopper and conveyed to the flow straightening mechanism. Thereafter, the inspection objects are aligned in a row by the flow straightening mechanism, and are discharged and passed to the first conveying device in such a state. A conveying speed of the first conveying device is set higher than a discharge speed of the flow straightening mechanism, and therefore, in the first conveying device, the inspection objects are conveyed in a state of being separated from each other at a predetermined interval depending on the difference between the speeds.
Thereafter, the inspection objects are conveyed with the upper surfaces thereof sucked and held by the second conveying device and the lower surfaces thereof are imaged by the first imaging device during the conveyance, and then they are conveyed with the lower surfaces thereof sucked and held by the third conveying device and the upper surfaces thereof are imaged by the second imaging device during the conveyance. The qualities of the upper and lower surfaces of each of them are judged by the sorting device from both of the captured images of the upper and lower surfaces, and the inspection objects conveyed by the third conveying device are sorted according to the judgment results.
Thus, according to the appearance inspection apparatus of the conventional example, it is possible to automatically inspect both of the upper and lower surfaces of each inspection object, and it is possible to automatically sorting the inspection objects into good products and defective products.